linux-kernel - Re: [PATCH v3 3/8] coccicheck: enable parmap support

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Message-ID: <alpine.DEB.2.02.1606212308580.2040@localhost6.localdomain6>
Date:	Tue, 21 Jun 2016 23:10:00 +0200 (CEST)
From:	Julia Lawall <julia.lawall@...6.fr>
To:	"Luis R. Rodriguez" <mcgrof@...nel.org>
cc:	Julia Lawall <julia.lawall@...6.fr>, Gilles.Muller@...6.fr,
	nicolas.palix@...g.fr, mmarek@...e.com,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	gregkh@...uxfoundation.org, markivx@...eaurora.org,
	stephen.boyd@...aro.org, zohar@...ux.vnet.ibm.com,
	broonie@...nel.org, ming.lei@...onical.com, tiwai@...e.de,
	johannes@...solutions.net, chunkeey@...glemail.com,
	hauke@...ke-m.de, jwboyer@...oraproject.org,
	dmitry.torokhov@...il.com, dwmw2@...radead.org, jslaby@...e.com,
	torvalds@...ux-foundation.org, deepa.kernel@...il.com,
	cocci@...teme.lip6.fr
Subject: Re: [PATCH v3 3/8] coccicheck: enable parmap support



On Tue, 21 Jun 2016, Luis R. Rodriguez wrote:

> On Tue, Jun 21, 2016 at 10:43:04PM +0200, Julia Lawall wrote:
> > 
> > 
> > On Tue, 21 Jun 2016, Luis R. Rodriguez wrote:
> > 
> > > On Tue, Jun 21, 2016 at 10:17:38PM +0200, Julia Lawall wrote:
> > > > 
> > > > 
> > > > On Tue, 21 Jun 2016, Luis R. Rodriguez wrote:
> > > > 
> > > > > Coccinelle has had parmap support since 1.0.2, this means
> > > > > it supports --jobs, enabling built-in multithreaded functionality,
> > > > > instead of needing one to script it out. Just look for --jobs
> > > > > in the help output to determine if this is supported.
> > > > > 
> > > > > Also enable the load balancing to be dynamic, so that if a
> > > > > thread finishes early we keep feeding it.
> > > > > 
> > > > > Note: now that we have all things handled for us, redirect stderr to
> > > > > stdout as well to capture any possible errors or warnings issued by
> > > > > coccinelle.
> > > > > 
> > > > > If --jobs is not supported we fallback to the old mechanism.
> > > > > This also now accepts DEBUG_FILE= to specify where you want
> > > > > stderr to be redirected to, by default we redirect stderr to
> > > > > /dev/null.
> > > > 
> > > > Why do you want to do something different for standard error in the parmap 
> > > > and nonparmap case?
> > > 
> > > We should just deprecate non-parmap later.
> > 
> > that's not really getting at the point.  I like the DEBUG_FILE= solution.  
> > I don't like merging stderr and stdout.  So you've put what to my mind is 
> > the good solution only in the deprecated case (to my understanding of 
> > the commit message).
> 
> stderr is not being merged to stdout though. By default stderr goes to /dev/null
> and if you want it you specify a DEBUG_FILE.

Above it says:

Note: now that we have all things handled for us, redirect stderr to 
stdout as well to capture any possible errors or warnings issued by 
coccinelle.

If DEBUG_FILE is an option for the parmap case, it should be mentioned 
there too.

julia



> 
> What will be deprecated has no clean solution for any of this and its unclear
> exactly what happens given separate processes are run in the background
> and we just wait.
> 
>   Luis
>